This invention relates to a scroll fluid apparatus, and, more particularly, to a scroll compressor, a scroll expander, a scroll pump, etc.
Generally, a scroll fluid apparatus comprises two scroll members each having an end plate and an upstanding wrap of a vortical form disposed on a surface of the end plate, with the two scroll members being arranged such that the wraps are in meshing engagement with each other. One of the two scroll members is capable of moving in orbiting movement with respect to the other scroll member while the one scroll member is prevented from rotating on its own axis whereby a gas is compressed or expanded to produce a motive force or transfer a liquid.
A scroll type fluid apparatus of the aforementioned type is disclosed, for example, in U.S. Pat. No. 801,182.
In, for example, U.S. Pat. No. 4,216,661 a fluid scroll apparatus of the aforementioned type is proposed wherein machining of the outer wall surface of the wrap of the stationary scroll member substantially for an extent of 180 degrees is unnecessary.
In a construction of the last-mentioned type, the time required for working the stationary scroll member can be shortened since there is no need to machine the outer wall surface of the wrap for an extent substantially of 180 degrees; however, a disadvantage of such construction resides in the fact that the surface normally machined contacts the end plate of the orbiting scroll member and the surface opposite thereto does not contact the end plate of the orbiting scroll member. Thus, the pressure acting on the orbiting scroll member becomes unbalanced, causing an unstable orbiting movement of the orbiting scroll member thereby giving rise to a problem of inducing vibration to occur in the orbiting scroll member.
Also, when the orbiting movement of the orbiting scroll member becomes unstable, it is impossible to keep the scroll fluid apparatus functioning at high efficiency for a prolonged period of time because the axial sealing of the orbiting scroll member and the stationary scroll member is adversely affected.